amblyopia vs vision defect

amblyopia and vision defect both are nouns.

Word	Noun	Adjective	Verb	Adverb
amblyopia	Yes	No	No	No
vision defect	Yes	No	No	No

As nouns, vision defect is a hypernym of amblyopia; that is, vision defect is a word with a broader meaning than amblyopia:

Other hypernyms of amblyopia include visual defect, visual disorder, visual impairment.

amblyopia (noun)	vision defect (noun)
visual impairment without apparent organic pathology	impairment of the sense of sight